Clean URL's: - Vs as a separator?

[brashquido]

Hi All,

I've read several articles around the web about clean URL structure and how they aid site usability, but I still can't decide on what separator I should be using. Currently I am using _ to separate words in my URL's, but most seem to be using - as the separator. I would appreciate feedback on the pros and cons of the following URL structures;

http://example.com/article/some_article_title

http://example.com/article/some-article-title

Cheers

[new_seo]

http://example.com/article/some-article-title

This one is perfect.Without a 2nd thought use this one.

[cmarshall]

I suspect that it is mostly up to the Web server. I think that they can all use "-" as a separator these days, and all OSes can use it.

I agree with new[-¦_]seo. ;)

[ogletree]

It has been the dash for a long time. There is some recent news that Matt Cutts says Google is now treating dash and underscore the same. SEO's are a superstitious bunch and we will probably stick with dashes until our last breath.